Orimura: A Novel Soft Pneumatic Actuator

This paper introduces Orimura, a novel soft pneumatic actuator inspired by a modified Yoshimura Origami cylinder, designed explicitly for substantial axial elongation. To identify an optimal configuration, eight variations of modified Yoshimura paper models were precisely evaluated. The actuator was fabricated by folding watercolor paper into an origami pattern and coating it with Ecoflex 00-50 elastomer, forming a flexible yet robust paper–elastomer composite. To ensure air-tightness, the structure was sealed with additional paper–elastomer layers. Actuation was achieved using a syringe pump: the actuator extended under positive pressure and contracted under vacuum. A mathematical model was developed to describe the relationship between the geometric parameters of the origami structure, specifically the varying row heights, and the resulting height ratio. This model was validated through a rigorous experimental testing process. Three Orimura configurations were fabricated and tested, demonstrating substantial axial elongation ranging from 262% to 638%. Notably, the largest actuator configuration with a cross-sectional area of 3375 mm2 achieved a maximum extension ratio of 638% while sustaining loads up to 15 times its weight without significant performance degradation. Even under a load 22 times its weight, the actuator maintained a considerable extension of 585%, indicating high load-bearing capacity. Significantly, the incorporation of paper reinforcement effectively suppressed lateral expansion during operation. Furthermore, the mathematical model suggests that even greater elongation may be achieved by increasing the actuator’s dimensions. These results underscore Orimura’s innovative structural design and its potential contribution to the development of customizable, high-performance actuators in the field of soft robotics.